A high frequency discharge excited CO.sub.2 laser has the following features:
(i) metallic electrodes and carbon dioxide gas (CO.sub.2) are not in contact with each other, so that no chemical reaction takes place therebetween;
(ii) being of capacitive ballast type, the laser has a high energy efficiency; and
(iii) since transverse electric discharge requires relatively low voltage, employment of a power source composed of a solid state device will do, so that the size of the equipment can be reduced.
For these reasons, the high frequency discharge excited CO.sub.2 laser can compose an oscillator which is
(i) small in size, and
(ii) high in efficiency.
However, transverse electric discharge is generaly used in the case of high frequency discharge excited and the resulting gain distribution over the cross section of laser tube does not have the circular symmetry. Accordingly, a high frequency discharge excited laser is used in combination with the transverse gas flow whose gain distribution similarly is not circular symmetry, wherefore a good beam mode is not to be expected. For this reason, a DC discharge excited coaxial type CO.sub.2 laser is used exclusively in the applications where good beam mode is a requirement. However, in respects other than beam mode, the DC discharge excited coaxial type laser is inferior to a high frequency discharge excited type laser.